1. Turn on the Instant Pot and select the 'Sauté' function. Add a bit of oil and cook the chicken until browned.
2. Add carrots, celery, onion, and cook until softened.
3. Pour in the chicken broth, salt, and pepper. Stir well.
4. Close the lid and set the Instant Pot to 'Manual' for 10 minutes.
5. While the soup is cooking, prepare the dumplings by mixing flour, baking powder, salt, milk, and melted butter in a bowl.
6. When the cooking time is up, quick release the pressure.
7. Drop spoonfuls of the dumpling mixture into the soup. Close the lid and cook on 'Manual' for another 5 minutes.
8. Quick release the pressure again, stir in the frozen peas, and serve hot.